KABUL — Schoolgirls sprayed with acid in southern Afghanistan had been warned not to go to school a week before the attack, a deputy minister said Wednesday.

Authorities have arrested 10 suspects in connection with the November 12 attack in which two men on a motorbike used a water pistol to spray acid on the girls as they arrived at school in the city of Kandahar.

They say the attack, which drew international condemnation, was the work of extremist Islamic Taliban, which barred girls from going to school when they were in government between 1996 and 2001.

"Evidence shows and witnesses say they (the girls) were threatened a week before not to go to school," deputy interior minister General Mohammad Daud told reporters in Kabul.

Daud said four of the 10 arrested men had confessed their involvement.

"The leader of the group and the person who sprayed the acid have confessed to their crimes. The confession of two others is still being studied," he said.

Eleven girls and four female teachers were in the group that was attacked and most were protected by their burkas, all-covering garments that most Afghan women wear in public.

Six girls were treated in hospital for burns. A 17-year-old girl was badly hurt and transferred to hospital in Kabul.

A state attorney told the same press conference courts would demand the highest punishment for the crime and that information showed the attack was "organised across Afghan borders", a reference to the tribal belt of Pakistan where Taliban and their Al-Qaeda allies have bases.

"This is Taliban and Al-Qaeda policy to fight culture and civilisation," said the lawyer, who is named only Mohibullah.

The Taliban have denied involvement, but the insurgents have most often been blamed for a series of attacks on Afghanistan's education system, with about 230 schools targetted in the year to June and dozens of people killed.

About half of the attacks have been on girls' schools even though they make up only 15 percent of schools in the country, according to a report to the UN Security Council this month.